Muffler with tuning tube

ABSTRACT

A muffler for silencing sound in gas, such as an exhaust system muffler, has a plurality of C-shaped tubes that are tuned to attenuate predetermined frequencies.

United States Patent 1 1 Plaga, III

[ v MUFFLER WITH TUNING TUBE [75] Inventor: Charles I. Plaga, Ill, Michigan Center, Mich.

[731 Assignee; Tenne co, lnc.,Racine, Wis;

22 Filed: 019.12, 1971 2'1 Appl. No.: 188,121

[51] Int. Cl. F0111 Ill") [58] Field of Search ..L 181/48, 54, 59, 61-63,

181/46, 56, 35 C, 36 B, 47' B, 36 D [56] References Cited UNITED STATES PATENTS 2,297,046 9/1942 Bourne 181/59 3,557,905 1/1971 1168....1.

[ June 19, 1973 3,434,565 4 3/1969 Fischer l8l/54 3,104,735 9/l963 Ludlow et al 181/48 2,199,164- 4 1940 Robbins 181 61 2,357,792 9/1944 Powers 1 1 181/48 3,031,026 4 1962 Price 181/5'4 3,198,284 8 1965 Powers 1 181 54 3,402,785 9 1968 Powers et al. 181 48 3,429,397 2/1969 Case...'. ..181 48 Primary Examiner-Richard B. Wilkinson Assistant Examiner-John F. Gonzales Attorney-Harness, Dickey & Pierce [57] ABSTRACT A muffler for silencing sound in gas, such as an exhaust system muffler, has a plurality of C-shaped tubes that are tuned to attenuate predetermined frequencies.

9 Claims, 4 Drawing Figures 1 MUFFLER WITH TUNING TUBE BRIEF SUMMARY OF THE INVENTION It is the purpose of this invention to provide an improved shape for a tuning tube useful in a muffler that silences .sound in flowing gas, such as an exhaust muffler.

The invention accomplishes this purpose by shaping the tuning tube in the form of a-C. so, that it may more readily fitin mufflers of asmall cross sectional area.

DESCRIPTION F THE DRAWINGS DESCRIPTION OF THE INVENTION I The muffler 1 has an outer housing or shell 3 which is preferably of circular cross section and relatively small in diameter. lt is reduced in diameter at each end and shaped to provide an inlet bushing 5 and an outlet bushing 7 which are preferably coaxial with the circular shape of the shell 3. The bushings 5 and 7 may be slotted as seen at .9 to facilitate the clamping of them to I other components of an internal combustion engine exhaust system, such as an exhaust pipe at the inlet end 5 and a tailpipe at the outlet end 7.

An open-ended straight-through flow tube 11 is mounted at one end in the bushing 5 and at the other end in the bushing 7 and is preferably spotwelded to one of the bushings as indicated at 13. The tube 11 has a bank of louvers or openings 15 formed in its wall adjacent the inlet bushing 5 and a second bank of louvers or openings 17 formed in its wall adjacent the outlet bushing 7. The banks 15 and 17 provide communication between the gas in the tube 11 and the chamber 19 which surrounds the tube inside theshell 3.

In accordance with this invention, a pair of arcuate or C-shaped tuning tubes 21 and 23 which are curved so as to be circular and concentric with the axis of the shell 3 and the tube 11 are mounted-on the outside of the tube so that they are nested in the space 119. The tubes 21 and 23 may be semi-circular and fit on the outside-of and be spotwelded to the tube 11 as seen in FIG. 2. In the muffler arrangement of FIG. 1, the tube 21, has an open end 25 thatis located just downstream of the louver bank 15 so that it communicates with the louver bank through'a short section of chamber 19.

The downstream end of the tube 21 is closed by a plug 27. The tube 23 is positioned sothat it has an open end 29 adjacent to the upstream end of the louver bank 17 and which can communicate with it through a short section of the chamber 19. The other end of the tube 23 is closed by a plug 31. The lengths of the tubes 21 and 23 are selected to enable the tubes to act as quarter wave length tuners to attenuate selected objectionable frequencies of sound found in the gas flowing through the muffler 21. The tubes '21 and 23 preferably fit around the outside of the tube 11 and are spotwelded to it. Their open ends are preferably located as close as .2: possible in the exhaust system" to the antinodes or maximum pressure points of 'the frequencieS and they are tuned to-attenuate, i. e. frequencies whose wave length is four times the length of the tube.

In operation, gas'enters the inlet bushing 5 and flows straight through the tube 11 to leave the muffler through the outlet bushing 9. Gas pressure pulses escape through louver banks 15 and 17 intothe chamber 19 where some attenuation occurs, particularly of the" high and medium frequencies. The length of the chamber 19 in conjunction with the louver banks can also act as a.- quarter wave length tuner in the event that there is an objectionable frequency with a wave length approximately four times the length of the shell 3. As indicated above, the lengths of the tubes 21 and 23 are one-quarter of the wave length of two different objectionable frequencies and they will, therefore, act upon pressure pulses entering the respective inlets 25 and 29 to attenuate such frequencies.

In the muffler'l0l of FIG. 4, the C-shaped tubes are used as Helmholtz tuning tubes instead of quarter wave length or Quincke tubes as in FIG. 1. In the muffler 101 there is a shell 103 having an inlet bushing 105 and an outlet bushing 107 in which is supported the straight through gas flow tube 111. A louver bank 1 17 adjacent the outlet end of the tube acoustically connects the gas in the tube to the chamber 119 within the shell 103.

C-shaped tuning tubes 121 and 123 are mounted on opposite sides of the flow tube 111 and are open at each end, a cross section through them being the same as FIG. 2. Their inlet ends 125 and 129, respectively, are adjacent the louver bank 117. Since the lengths of the tubes 121 and 123 are substantially different, and since each opens into a common chamber 1 19, it is apparent that the two tubes in conjunction with the volume of chamber 119 will be tuned under the Helmholtz formula to attenuate different frequencies since their cross sectional-areas are the same. Accordingly, in operation, the tubes will function to attenuate different desired frequencies in accordance with the frequencies for which their lengths have been chosen. Preferably, a transverse partition 131 adjacent the inlet ends of the tubes separates the resonator chamber 119 from the louver chamber 133 that receives pressure pulses from the louver bank 117 and feeds the tuners 121 and 123. Thus, the only inlets and outlets to the chamber 119 are via the tuning tubes.

It is apparent that the arcuate shape. of the tuning tubes 21 and 23 or 121 and 123 enables them to fit neatly inside a shell 3 of 103 that is very small in diameter and cross sectional area and that they uniquely enable such a small shell to house meansto attenuate very low frequencies. 7

Modifications may be made without departing-from the spirit and scope of the invention. For example, in FIG.-4 one of the tubes 121 or 123 could be closed at the outletend to make it a quarter wave tuner as in the muffler-l whereby the muffler would contain one C- shaped tube as a Helmholtz tuning tube and one as a quarter wave tuner.

I claim:

1. In a gas silencing muffler an elongated housing of circular cross section, an elongated gas fiow tube of circular cross section extending through the housing and coaxial with the housing, and elongated tubular sound attenuating tube extending parallel to the gas flow tube 'and located betyveen the gas flow tube and the housing,

sound attenuating tube is closed at one end and serves I as a quarter wave length tuning tube.

3. A muffler as set forth in claim 1 including a second elongated tubular sound attenuating tubeof substantially C-shaped cross section and curved substantially about the axis of the housing and flow tube and located in the space between the flow tube and the housing and substantially opposite to the first mentioned sound'attenuating tube. I

4. A'muffler as set forth in claim 3 wherein said two C-shaped tubes are substantially semi-circular in shape.

5. A muffler as set forth in claim 4 wherein said C- shaped tubes are mounted on and secured to the gas flow tube on opposite sides thereof.

6. A muffler as set forth in claim 1 including means providing a sound attenuating chamber in the housing,

said sound attenuating tube being open at one end in said chamber and at the other en'd being open to and in communication with gas flowing through the gas flow tube,-said sound attenuating tube and said chamber being interrelated in accordance with the Helmholtz formula to provide attenuation of a predetermined sound frequency.

7. A muffler as set forth in claim 7 including a second elongated tubular sound'attenuating tube of substantially C-shaped cross section and curved substantially about the axis of the housing and flow tube and locatedin the space between the flow tube and the housing and substantially opposite to the first mentioned sound attenuating tube.

8. A muffler as set forth in claim 7 wherein said second tube is open at one end in said chamber and at the other end is open to and in communication with gas flowing through the gas flow tube.

9. A muffler as set forth in claim 7 wherein said second tube is closed at one end and serves as a quarter wave lengthtuning tube. v 

1. In a gas silencing muffler an elongated housing of circular cross section, an elongated gas flow tube of circular cross section extending through the housing and coaxial with the housing, and elongated tubular sound attenuating tube extending parallel to the gas flow tube and located between the gas flow tube and the housing, said sound attenuating tube being substantially C-shaped in cross section and curved substantially about the axis of the housing and flow tube and being in operative communication with gas flowing through the gas flow tube.
 2. A muffler as set forth in claim 1 wherein said sound attenuating tube is closed at one end and serves as a quarter wave length tuning tube.
 3. A muffler as set forth in claim 1 including a second elongated tubular sound attenuating tube of substantialLy C-shaped cross section and curved substantially about the axis of the housing and flow tube and located in the space between the flow tube and the housing and substantially opposite to the first mentioned sound attenuating tube.
 4. A muffler as set forth in claim 3 wherein said two C-shaped tubes are substantially semi-circular in shape.
 5. A muffler as set forth in claim 4 wherein said C-shaped tubes are mounted on and secured to the gas flow tube on opposite sides thereof.
 6. A muffler as set forth in claim 1 including means providing a sound attenuating chamber in the housing, said sound attenuating tube being open at one end in said chamber and at the other end being open to and in communication with gas flowing through the gas flow tube, said sound attenuating tube and said chamber being interrelated in accordance with the Helmholtz formula to provide attenuation of a predetermined sound frequency.
 7. A muffler as set forth in claim 7 including a second elongated tubular sound attenuating tube of substantially C-shaped cross section and curved substantially about the axis of the housing and flow tube and located in the space between the flow tube and the housing and substantially opposite to the first mentioned sound attenuating tube.
 8. A muffler as set forth in claim 7 wherein said second tube is open at one end in said chamber and at the other end is open to and in communication with gas flowing through the gas flow tube.
 9. A muffler as set forth in claim 7 wherein said second tube is closed at one end and serves as a quarter wave length tuning tube. 